1. Lesson 5-2
Cycloalkanes
Alkanes that form rings are called cycloalkanes.
Cyclopropane and cyclobutanes are strained because the C-C-C bond angles in the ring are less than 109.5 required for the tetrahedral geometry.
Because of the strain in the ring, cyclopropane is very reactive.

3. Examples – Name the following:1.
cyclohexane 2.
cycloheptane

4. Substituted Cycloalkanes
Examples: Name each compound
1-ethyl-4-methylcycloheptane
2-ethyl-1,1-dimethylcyclobutane

5. Unsaturated Hydrocarbons
Unsaturated hydrocarbons contain double bonds or triple bonds between carbon atoms.
For each double bond, there are two less hydrogen atoms (than CnH2n+2)
For each triple bond, there are four less hydrogen atoms (than CnH2n+2)

6. Alkenes – contain C=C double bond(s).
Named like alkanes, except the ending is changed to “ene.”
You must number the carbon atom on which the double bond “begins.”
Example:
Pent-2-ene What is the formula?
More Examples
2-methylhex-2-ene 5-ethyl-3-methylhept-2-ene

7. Alkynes – contain C=C triple bond(s).
Named like alkanes, except the ending is changed to “yne.”
You must number the carbon atom on which the triple bond “begins.”
Example:
Hex-2-yne
Another Example:
2,6-dimethyloct-3-yne

8. Properties of Unsaturated Hydrocarbons
Alkenes and alkynes are generally nonpolar, and contain only LDF.
A carbon atom bonded to four other atoms has tetrahedral geometry.
A carbon atom bonded to three other atoms has trigonal planar geometry.
A carbon atom bonded to two other atoms has linear geometry.

9. Functional Groups
Some organic molecules contain elements other than just C and H.
The parts of the molecules that are elements other than C and H are called functional groups.
Alcohols – contain –OH in place of one or more hydrogen atoms.
Named like the hydrocarbon on which they are based (# C atoms), with –ol in place of the e. Begin with the number of the C that contains the OH

10. Examples – Name the following alcohols
ethanol
1-hexanol
2-methyl-3-hexanol

11. Reactions of Alcohols
1. Oxidation – warmed with acidified dichromate (Cr2O72-)
Primary alcohols (C with OH is attached to one other C)
oxidized to aldehydes, then to carboxylic acids.
Secondary alcohols (C with OH is attached to 2 other C)
oxidized to ketones
Tertiary alcohols (C with OH is attached to 3 other C – no H atoms attached to C with OH)
cannot be oxidized by dichromate

12. Dehydration (in concentrated sulfuric or phosphoric acid) – produces a double bond (opposite of addition of water)